The present invention relates to a contact structure for a switch and a method for manufacturing a switch contact.
A switch known in the prior art has a contact structure including a fixed contact, which is arranged on a substrate, and a movable contact opposing the fixed contact. The movable contact is engaged with and disengaged from the fixed contact when the switch performs a switching operation. In the contact structure of this switch, a foreign material may get caught between the fixed contact and the movable contact. This may obstruct the engagement of the movable contact with the fixed contact and thus impede the flow of current between the movable and fixed contacts.
To solve this problem, Japanese Laid-Open Patent Publication No. 2001-126565 describes a contact structure for a switch that uses a movable contact formed by a rubber member. A conductive film is applied to both upper and lower surfaces of the rubber member. Metal wires connecting the conductive films are embedded in the rubber member. When there is a layer of foreign material between the fixed contact and the movable contact, the metal wires penetrate the foreign material layer and contact the fixed contact. Thus, the metal wires stably ensure electrical connection between the fixed contact and the movable contact.
The metal wires penetrate foreign material layers deposited on the fixed contact and ensure electrical connection between the fixed and movable contacts. However, once a layer of foreign material is deposited on the fixed contact, the metal wires would have to penetrate the foreign material layer whenever force is applied to the metal wires of the movable contact. This would cause wear of the metal wires and decrease durability. Further, the amount of foreign material deposited on the fixed contact may increase. This would increase the thickness of the foreign material layer deposited on the fixed contact. When the thickness exceeds a certain value, the metal wires would not be able to penetrate the foreign material layer. In such a case, normal switching operations cannot be performed.